The present invention relates generally to an analysis instrument, and more particularly to an analysis instrument which is adapted to measure the quantities of specific constituents present in bulk commodities such as agricultural products, as for example, corn, soy beans and the like. Still more particularly, the present invention is directed to an improved analysis instrument for measuring and analyzing optical properties, as for example, optical density, of materials at various frequencies to determine the quantities of certain constituents present in the materials.
Traditional analytical and laboratory techniques for measuring the quantities of constituents present in various materials, as for example, the quantities of moisture, protein or oils present in various agricultural grain products, require the use of relatively complex equipment as well as the efforts of skilled chemists or other skilled technicians. Many users of agricultural products, however, are increasingly interested in obtaining such data as the percentages of moisture, protein and oil contained in these products. Specifically, the practice of selling wheat on the basis of a guaranteed protein content has become widespread. In order to remain competitive, the commodity handler must be able to rapidly and accurately sort grains and other products by their content of various constituents, when such data is specified by the users. Thus, there is a need for a versatile test instrument for rapidly determining the quantity of various constituents present in actual samples of various commodities. Such an instrument must be capable of reliably testing a relatively broad range of materials for a number of constituents, while being relatively easy to operate so that the operator thereof need not possess specialized skills or specific knowledge of the theory or function of the instrument.
An analysis of the optical densities of various materials as, for example, by non-destructive light transmittance or reflectance tests, is indicative of the content of various constituents present in the materials. For example, the amount of light reflected at certain frequencies from a sample of a farm grain is indicative of the content thereof of such constituents thereof as moisture, protein, and oil. The difference in optical density of the material as determined by the ratio of amount of light reflected therefrom to amount of light incident thereon measured at two different frequencies has been found to be a useful measurement in determining various constituent contents. Specifically, the constituent content of the material is a function of the difference in optical density so measured. If the intensity of incident light at both frequencies is held constant, then the difference in optical density may be determined from the difference in reflected light intensities at the two frequencies. Certain frequencies may be selected for their sensitivity to specific constituents and the optical densities at these various specific frequencies are interrelated, such that the content of a plurality of constituents may be determined by correlating measurements taken at frequencies selected for each.
Accordingly, it was necessary in prior art devices to have a large number of frequencies or wavelengths of infrared radiation made available via either a large array of filter elements for passing individual wavelengths from a fixed source or via relatively complex mechanical structures for rotating a number of fixed filters through a variety of angular positions with respect to a light source to obtain varying frequencies therefrom. It will be appreciated that the complexity of the mechanical parts required to handle either such a large number of filter elements or a relatively complex rotation and movement of filter elements, is cumbersome and difficult to manufacture and to properly install, giving rise to excessive expense and potential unreliability of the instrument. Also, prior instruments generally have been designed, constructed and calibrated so as to be capable of handling only a predetermined fixed number of grains and of obtaining readings therefrom representative of only a limited number of constitutents thereof, commonly being limited to percentage content of oil, water and protein. As a practical matter, therefore, it is not possible to expand the capabilities of such prior art instruments to perform measurements on different materials or to measure different constituents than those for which they are already designed. Further, prior art instruments are also subject to temperature variation. For example, changes in the temperature of the optical portions of the instruments, including the filters and the sensors, can cause difficulty in maintaining reliability in measurements performed over a range of temperatures.